Investigating the disorder–order transition of calmodulin binding domain upon binding calmodulin using molecular dynamics simulation

We have studied the conformational transition of the calmodulin binding domains (CBD) in several calmodulin‐binding kinases, in which CBD changes from the disordered state to the ordered state when binding with calmodulin (CaM). Targeted molecular dynamics simulation was used to investigate the binding process of CaM and CBD of CaM‐dependent kinase I (CaMKI–CBD). The results show that CaMKI–CBD began to form an α‐helix and the interaction free energy between CaM and CaMKI–CBD increased once CaM fully encompassed CaMKI–CBD. Two series of CaM/CBD complex systems, including the complexes of CaM with the initially disordered and the final ordered CBD, were constructed to study the interaction using molecular dynamics simulations. Our analyses suggest that the VDW interaction plays a dominant role in CaM/CBD binding and is a key factor in the disorder–order transition of CBD. Additionally, the entropy effect is not in favor of the formation of the CaM/CBD complex, which is consistent with the experimental evidence. Based on the results, it appears that the CBD conformational change from a non‐compact extended structure to compact α‐helix is critical in gaining a favorable VDW interaction and interaction free energy. Copyright © 2009 John Wiley & Sons, Ltd.     

Differences between karyotypically normal and abnormal human embryonic stem cells

Objectives: To compare different biological characteristics of human embryonic stem cells (HESCs) between those with normal and those with abnormal karyotype. Materials and methods: Culture‐adapted HESCs (chHES‐3) with abnormal karyotype were compared with karyotypically normal cells, with regard to pluripotency and differentiation capacity, ultrastructure, growth characteristics, gene expression profiles and signalling pathways. Results: We found a new abnormal karyotype of HESCs. We observed that chHES‐3 cells with normal and abnormal karyotypes shared similarities in expression markers of pluripotency; however, karyotypically abnormal chHES‐3 cells had a tendency for differentiation towards ectoderm lineages and were easily maintained in suboptimal culturing conditions. Abnormal chHES‐3 cells displayed relatively mature cell organelles compared to normal cells, and karyotypically abnormal chHES‐3 cells had increased survival and population growth. Genes related to cell proliferation and apoptosis were up‐regulated, but genes associated with genetic instability (p53, Rb, BRCA1) were down‐regulated in the karyotypically abnormal cells. Conclusion: Karyotypically abnormal chHES‐3 cells had a more developed capacity for proliferation, resistance to apoptosis and less genetic stability compared to normal chHES‐3 cells and may be an excellent model for studying and characterizing initial stages that determine transition of embryonic stem cells into cancer stem cells.     

A glycerol-free process to produce biodiesel by supercritical methyl acetate technology: An optimization study via Response Surface Methodology

In this study, fatty acid methyl esters (FAME) have been successfully produced from transesterification reaction between triglycerides and methyl acetate, instead of alcohol. In this non-catalytic supercritical methyl acetate (SCMA) technology, triacetin which is a valuable biodiesel additive is produced as side product rather than glycerol, which has lower commercial value. Besides, the properties of the biodiesel (FAME and triacetin) were found to be superior compared to those produced from conventional catalytic reactions (FAME only). In this study, the effects of various important parameters on the yield of biodiesel were optimized by utilizing Response Surface Methodology (RSM) analysis. The mathematical model developed was found to be adequate and statistically accurate to predict the optimum yield of biodiesel. The optimum conditions were found to be 399 °C for reaction temperature, 30 mol/mol of methyl acetate to oil molar ratio and reaction time of 59 min to achieve 97.6% biodiesel yield.     

A stereo-controlled synthesis of 2,4-dimethyl-4-hydroxy-16-phenylhexadecanoic acid 1,4-lactone and its PPAR activities

A novel class of natural PPAR agonists, 2,4-dimethyl-4-hydroxy-16-phenylhexadecanoic acid 1,4-lactone (1), were discovered in marine natural product libraries. The synthesis of 1 was accomplished starting from vinylmethyl ketone. Ring formation of the α,γ dialkyl γ-lactone was achieved via the stereo-controlled reaction of a ketyl radical anion with a chiral methacrylate. In the PPAR agonistic assay, the most potent of the four stereoisomers had EC₅₀ values of 12 μM for mPPARα, 9 μM for mPPARδ and >100 μM for mPPARγ.     

Design and synthesis of piperazine-indole p38α MAP kinase inhibitors with improved pharmacokinetic profiles

Derivatives of the 4-fluorobenzyl dimethylpiperazine-indole class of p38α MAP kinase inhibitors are described. Biological evaluation of these compounds focused on maintaining activity while improving pharmacokinetic (PK) properties. Improved properties were observed for structures bearing substitutions on the benzylic methylene.     

Synthesis and evaluation of alkenyl indazoles as selective Aurora kinase inhibitors

A series of alkenyl indazoles were synthesized and evaluated in Aurora kinase enzyme assays. Several promising leads were optimized for selectivity towards Aurora B. Excellent binding affinity and good selectivity were achieved with optimized compounds in isolated Aurora subfamily assays.     

生长因子诱导人脐带/胎盘间充质干细胞定向分化

近年来,间充质干细胞(mesenchymal stem cell,MSC)已成为干细胞领域的研究热点,其不仅支持造血系统,还可在特定的培养条件下向多种组织细胞分化。人脐带和胎盘来源的MSC取材容易,较骨髓间充质干细胞有更广泛的应用前景。本文就含有特定生长因子的培养基诱导人脐带MSC和人胎盘MSC定向分化的研究进展作一简要的综述。     

Hormonal regulation of uterine natural killer cells in mouse preimplantation uterus

Uterine Natural Killer (uNK) cells are the most abundant lymphocyte population recruited in the uteri during murine and human pregnancy. Previous investigation on uNK cells during mouse pregnancy focused more on its accumulation in postimplantation periods, which were believed to play important roles in regulating trophoblast invasion and angiogenesis towards successful placentation. However, by using recently developed methods of Dolichos biflorus agglutinin (DBA) lectin, a closer examination during mouse preimplantation revealed that there were also dynamic regulations of uNK cell, suggesting a major regulation by steroid hormones. Here we provide a detailed examination of uNK cells distribution during mouse early pregnancy by DBA lectin reactivity, with emphasis on preimplantation period and its hormonal regulation profiles. Our results showed that uNK precursor cells or its cell membrane specific components could be recruited in the uterus by estrogen or/and progesterone, and the effects could be completely abolished by specific antagonists of their nuclear receptors (estrogen and progesterone receptor). These results suggested that the preimplantation uterus, through concerted hormone regulation, could recruit uNK precursor cell or its specific cellular component, which might be conducive for uterine receptivity and further uNK construction/function during postimplantation.     

Metabolic flexibility and cell hierarchy in metastatic cancer

Cancer is characterized by disturbed homeostasis of self-renewing cell populations, and their ability to seed and grow in multiple microenvironments. This overarching cellular property of metastatic cancer emerges from the contentious cancer stem cell hypothesis that underpins the more generic hallmarks of cancer (Hanahan and Weinberg, 2000) and its subsequent add-ons. An additional characteristic, metabolic flexibility, is related to concepts developed by Warburg and to subsequent work by mid 20th century biochemists who elucidated the bioenergetic workings of mitochondria. Metabolic flexibility may circumvent limitations inherent in the increasingly popular but erroneous view that aerobic glycolysis is a universal property of cancer cells. Cancer research in the second half of the 20th century was largely the domain of geneticists and molecular biologists using reductionist approaches. Integrated approaches that address cancer cell hierarchy and complexity, and how cancer cells adapt their metabolism according to their changing environment are now beginning to emerge, and these approaches promise to address the poor mortality statistics of metastatic cancer.